Critical Slowing Down from $T\neq 0$ Wilson RG

Abstract

The Thermal Renormalization Group can be employed to study the dynamics of $T\neq 0$ Quantum Field Theories close to second order phase transitions, where neither resummed perturbation theory nor first principle lattice simulations can be employed. As an example, I discuss the computation of the plasmon damping rate in the scalar field theory from $T\gg T_C$ down to $T_C$. As the critical point is approached, the lifetime of long wavelength thermal fluctuations diverges. Taking this effect into account, the notion of quasiparticle, and kinetic approaches, can be extended close to the critical regime. The consequences on the scenarios for topological defect formation in the early universe are also discussed.